Study on Deoxidations during VIM Refining Ni-base Superalloy by Using CaO Crucible

The changes of carbon and oxygen contents and the influence of carbon and aluminium on deoxidation during vacuum induction melting (VIM) refining Ni-6Cr-2Mo-6W-5Co alloy using CaO crucible were studied. The results show that carbon play significant role on deoxidation during the melting stage, and about 40 to 80 percents of oxygen can be reduced. Aluminium addition can further decrease oxygen content to 0.0004%~0.0006%. The equilibrium values of C-O and Al-O reactions in liquid alloy were calculated from thermodynamics. The results demonstrate that C-O reaction is far from equilibrium status. Al-O reaction can further decrease oxygen content to below 0.0006%.